yesterdagel Share definition Flag A day old bagel. It's not as good as a fresh bagel, but if you toast it and slather it with cream cheese, it'll do in a pinch. I nearly broke my tooth eating a yesterdagel this morning. yesterdagel by Saucy Lady October 23, 2009 0 0 Get merch Get the yesterdagel mug. Buy Now — $32.95 See more merch